A new determination of \alpha_s from hadronic \tau\ decays

TL;DR

This paper introduces a new method using finite-energy sum rules and a quantitative model to extract the strong coupling constant _s from hadronic  decays, accounting for non-perturbative effects and quark-hadron duality violations.

Contribution

It presents a novel framework that improves the extraction of _s by modeling non-perturbative effects and duality violations in  decay data analysis.

Findings

_s(m_ au^2)=0.307b1 0.019 (fixed-order)

_s(m_ au^2)=0.322b1 0.026 (contour-improved)

Results are consistent with previous analyses but include a more comprehensive treatment of uncertainties.

Abstract

We present a new framework for the extraction of the strong coupling from hadronic \tau decays through finite-energy sum rules. Our focus is on the small, but still significant non-perturbative effects that, in principle, affect both the central value and the systematic error. We employ a quantitative model in order to accommodate violations of quark-hadron duality, and enforce a consistent treatment of the higher-dimensional contributions of the Operator Product Expansion to our sum rules. Using 1998 OPAL data for the non-strange isovector vector and axial-vector spectral functions, we find the n_f=3 values \alpha_s(m_\tau^2)=0.307+-0.019 in fixed-order perturbation theory, and 0.322+-0.026 in contour-improved perturbation theory. For comparison, the original OPAL analysis of the same data led to the values 0.324+-0.014 (fixed-order) and 0.348+-0.021 (contour-improved).